Drive unit for a centrifuge rotor of a centrifugal separator

ABSTRACT

A drive unit for a centrifuge rotor of a centrifugal separator is provided that includes a drive shaft, arranged to support the centrifuge rotor and rotatably journalled around an axis (z) of rotation, a casing, which forms an inner space for the drive shaft, a drive motor shaft which is provided outside the casing and connected to the drive shaft by means of a transferring member extending through a passage in the casing, at least one shielding member, which is provided inside the casing in such a manner that the part of the transferring member which is located inside the casing is shielded from the inner space, and wherein the shielding member forms a channel, which extends through the casing and is shielded from the inner space of the casing.

FIELD OF THE PRESENT INVENTION

Background of the Present Invention

The present invention refers to a drive unit for a centrifuge rotor of acentrifugal separator, wherein the drive unit includes a drive shaft,which is arranged to support said centrifuge rotor and rotatablyjournalled around an axis of rotation in at least one first bearingmember, a casing, which forms an inner space for the drive shaft andsaid bearing member, and a drive motor, which is provided outside thecasing and connected to the drive shaft by means of a transferringmember extending through a passage in the casing.

In order to cool the bearings supporting the drive shaft in such a driveunit, it is known to re-circulate an air stream which, by means ofaccompanying oil droplets, forms an oil mist through the bearings andthe inner space defined by the casing. Such drive units frequentlyinclude a drive belt for transferring the rotation of the drive motor tothe drive shaft of the centrifuge rotor. In the cases that the drivemotor is located outside the casing, the drive belt will either engagethe drive shaft beneath the casing or extend through an opening in thecasing. In order to prevent, in the latter case, oil from penetratingthe environment and contacting the drive belt, the opening has to besealed with respect to the drive belt. It has proved to be difficult toprovide such an effective sealing. According to another solution, thedrive motor may be provided inside the casing. However, this solutionrequires such an enclosure of the drive motor that oil is prevented frompenetrating the drive motor and destroying the latter.

Another problem in this connection is the removal of the heat absorbedby the oil mist during its passage through the bearings, which supportthe drive shaft of the centrifuge rotor.

SUMMARY OF THE INVENTION

The object of the present invention is to remedy the problems mentionedabove and provide a drive unit enabling a satisfactory sealing of theinner space of the casing with respect to the environment and enablingan effective cooling of the oil mist which is re-circulated in the innerspace of the casing.

This object is obtained by the drive unit initially defined, which ischaracterised by a shielding member provided inside the casing in such amanner that the part of the transferring member which is located insidethe casing is shielded from the inner space. Despite the fact that apart of the transferring member is located inside the casing, the wholetransferring member, for instance in the form of a drive belt, will thusbe separated from the inner space defined by the casing. No sealing ofthe transferring member is thereby required. Furthermore, such ashielding member enables an effective cooling of the different drivingcomponents by means of the surrounding air. The shielding member alsocreates a relatively large cooling surface extending in the inner spaceof the casing and thus contributes to the cooling of the oil mist, whichis re-circulated in the inner space of the casing. Advantageously, theshielding member forms a channel, which extends through the casing andis shielded from the inner space of the casing.

According to an embodiment of the invention, the shielding memberincludes an upper opening and a lower opening, wherein the drive shaftextends through the shielding member through these openings. Sealingmembers may thereby be provided between the drive shaft and saidopenings. Thereby, the interior of the casing may, in an easy manner, besealed from the environment and oil may be prevented from reaching theenvironment and the drive belt.

According to a further embodiment of the invention, the shielding memberis connected to the casing by a connection extending around saidpassage. Furthermore, the shielding member may have an elongated shapewith a longitudinal axis extending substantially radially with respectto the axis of rotation. The shielding member extends substantiallydiametrically through the casing with respect to the axis of rotation.

According to a further embodiment of the invention, the transferringmember includes a drive belt which engages the drive shaft via a beltpulley provided on the drive shaft and thus located inside the shieldingmember. Such a drive belt will contribute to the creation of an air flowthrough the channel, thereby making the cooling more efficient. A wallmember may thereby be substantially centrally provided in said channelin such a way that the channel is divided into two partial-channels andthe drive belt may run inwardly in one of the partial-channels andoutwardly in the other partial-channel. In such a manner, a first airflow from the environment will flow inwardly in one of thepartial-channels and a second air flow will flow outwardly through theother partial-channel. The wall member extends in a substantially axialand radial plane with respect to the axis of rotation from an area inthe proximity of the belt pulley to an area in the proximity of saidpassage. The drive shaft may be rotatably journalled in at least onebearing member located radially inside the drive belt.

According to a further embodiment of the invention, the transferringmember includes a drive belt which engages the drive shaft via a beltpulley provided on the drive shaft and thus located inside the shieldingmember. Such a drive belt will contribute to the creation of an air flowthrough the channel and thereby making the cooling more efficient.Advantageously, a wall member may thereby be substantially centrallyprovided in said channel in such a way that the channel is divided intotwo part-channels and the drive belt may run inwardly in one of thepart-channels and outwardly in the other part-channel. In such a manner,a first air flow from the environment will flow inwardly in one of thepart-channels and a second air flow will flow upwardly through the otherpart-channel. Advantageously, the wall member extends in a substantiallyaxial and radial plane with respect to the axis of rotation from an areain the proximity of the belt pulley to an area in the proximity of saidpassage. The drive shaft may be rotatably journalled in at least onebearing member located radially inside the drive belt.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by adescription of an embodiment and with reference to the drawingsattached, in which

FIG. 1 discloses schematically a partly sectional perspective view of adrive unit for a centrifuge rotor of a centrifugal separator, and

FIG. 2 discloses a sectional view through a lower part of the drive unitin FIG. 1.

FIG. 3 is an enlarged partial cross-sectional view of the drive unit ofFIG. 2 corresponding to the area enclosed by the circle labelled A inFIG. 2.

FIG. 4 is an enlarged partial cross-sectional view of the drive unit ofFIG. 2 of the area enclosed by the circle labelled B in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 discloses a drive unit 1 for a partly disclosed centrifuge rotor2. The drive unit 1 and the centrifuge rotor 2 form together essentialcomponents of a centrifugal separator. The drive unit 1 includes a driveshaft 3, which supports the centrifuge rotor 2 and is rotatable aroundan axis z of rotation and carried by means of a first, upper bearingmember 4 and a second, lower bearing member 5, see FIG. 2. Furthermore,the drive unit 1 includes a casing 6 delimiting an inner space. Theinner space consists of an upper space 7, in which the drive shaft 3,the first bearing member 4, and the second bearing member 5 are located,as well as a lower space 8, which is designed as an oil sump andarranged to contain a quantity of liquid oil. The drive unit 1 alsoincludes a drive motor (not disclosed) which is connected to a beltpulley 9. The drive motor and the belt pulley 9 are provided outside thecasing 6 and connected to a belt pulley 10 fixedly attached to the driveshaft 3 by means of a transferring member in the form of a drive belt 11extending through a passage 12 in the casing 6. It is to be noted thatthe drive belt 11 may be replaced by a drive shaft which, via twobearings, drivingly engages the drive motor and the drive shaft 3.

The upper bearing member 4, the so-called neck bearing, is carried bymeans of the bearing housing 13. The bearing housing 13 is connected toa first shielding member 14 including at least one shielding portion,which extends outwardly, preferably substantially radially outwardly,from the upper bearing member 4 in a direction towards an inner wall ofthe casing 6. The bearing housing 13 and the shielding member 14 are, inthe example disclosed, designed to form a space 15, which is intended toreceive dampening elements (not disclosed) known per se. The upperbearing member 4 is connected to the casing 6 via the bearing housing13, said dampening elements and the first shielding member 14.

A second shielding member 16 extends substantially axially downwardlyfrom a radially outer edge of the first shielding member 14 between thedrive shaft 3 and an inner wall of the casing 6 in such a way that anannular passage 17 is formed therebetween. The second shielding member16 extends in the example disclosed around the drive shaft 3 and so fardownwardly that a relatively thin gap is formed between a lower edge ofthe second shielding member 16 and the oil in the lower space 8.

In the example disclosed, the drive shaft 3, see FIG. 2, extends throughthe upper space 7 and downwardly into the oil in the lower space 8.Furthermore, the drive shaft 3 includes an inner channel 18, which hasat least one orifice in the lower space 8 and a plurality of orifices 19in the upper space 7 above the belt pulley 10 but below the upperbearing member 4. The drive shaft 3 is designed in such a way that oilis transported through the inner channel 18 during operation of thecentrifugal separator and forms small oil droplets at least at the exitof the oil from the upper orifices 19.

Furthermore, the drive unit 1 includes a fan wheel 20 which is fixedlyprovided on the drive shaft 3, in the example disclosed above the upperbearing member 4. The fan wheel 20 is arranged to drive a flow of airand oil droplets, which form an oil mist flowing through the upperbearing member 4 for cooling and lubricating thereof. Furthermore, thefan wheel 20 is arranged to drive said flow from an outlet of the upperbearing member 4 radially outwardly in a direction towards the innerwall of the casing 6 and axially downwardly through the passage 17between the inner wall of the casing 6 and the second shielding member16 to a position immediately above the oil in the lower space 8, i.e. tosaid gap between the second shielding member 16 and the oil in the lowerspace 8. A part of the oil, which is present in said flow, will therebybe collected by the oil in the lower space 8 and a part of the oil willbe transported further by the air stream upwardly through the lowerbearing member 5 in such a way that also the latter is cooled andlubricated, which is described more closely below. From an outlet of thelower bearing member 5, the oil mist is transported further through anumber of channels 21, which extend through the belt pulley 10, up to aninlet of the upper bearing member 4. An air stream containing oildroplets will thus be re-circulated as an oil mist in a path in theinner space 7, 8 defined by the casing 6, which extends through theupper and lower bearing members 4, 5 and the passage 17 where the oilmist looses its heat and is cooled by contacting the inner wall of thecasing 6. In order to increase the cooling of the oil mist, flanges 22or any similar surface-increasing members may be provided on the outerwall of the casing 6. FIG. 1 discloses as an example one such flange 22.Such flanges or any similar surface-increasing members may also beprovided on the inner wall of the casing 6 and/or on the secondshielding member 16.

It is to be noted that the passage 17 may be realized in many differentmanners. For instance, the passage may be formed by conduits extendingsubstantially vertically outside the casing 6 by means of openings inthe upper and lower parts of the casing 6. Such external conduits may becooled in an efficient manner by the air of the environment. The passagemay also be formed by channels extending substantially vertically in thewall of the casing 6 from an upper part of the casing 6 to a lower partthereof. In these embodiments, the second axial shielding member 16 maybe dispensed with. The passage 6 may also be designed as a number ofseparate channels extending substantially vertically inside the innerwall of the casing 6. In such an embodiment, the second shielding member16 may be formed by a plurality of shielding members, for instance aseparate shielding member for each such separate channel.

Furthermore, the drive unit 1 includes a shielding member 23, which isprovided in such a casing 6 and which is arranged to house the part ofthe drive belt 11 which extends inside the casing 6 in such a way thatthe drive belt 11 is shielded from the inner space 7, 8 of the casing 6.The shielding member 23 is connected to the inner wall of the casing 6at two diametrically opposed sides by means of a respective connectionextending around the passage 12 mentioned above and diametricallyopposite passage 24. Consequently, the shielding member 23 forms achannel 25 which extends substantially diametrically through the innerspace 7, 8 of the casing 6 with respect to the axis z of rotation andwhich is shielded from this inner space 7, 8. Furthermore, the shieldingmember 23 has an elongated, box-like shape, i.e. it is substantiallyrectangular seen in the cross-sectional view disclosed in FIG. 2, andincludes an upper limiting wall and a lower limiting wall, which aresubstantially parallel to each other, and two substantially parallellateral limiting walls. It is to be noted that the shielding member 23also may have another cross-sectional shape than a rectangular one, itmay, for instance, be oval.

Furthermore, the shielding member 23 includes an upper opening 26, whichextends through the upper limiting wall, and a lower opening 27, whichextends through the lower limiting wall. The drive shaft 3 extendsthrough the shielding member 23 through these openings 26, 27, whereinthe upper opening 26 also is arranged to receive an upper part of thebelt pulley 10. As indicated in FIG. 2, a gap seal 28, for instance alabyrinth seal, is provided between the belt pulley 10 and the upperlimiting wall of the shielding member 23. The lower limiting wall of theshielding member 23 includes a circular cylindrical portion 29, whichforms the lower opening 27. The circular cylindrical portion 29 carries,as appears from FIG. 2, the lower bearing member 5. Furthermore, thecircular cylindrical portion 29 extends in a circular cylindrical recess30 of the belt pulley 10. Between the outer surface of the cylindricalportion 29 and the inner surface of the circular cylindrical recess 30 agap seal 31 is provided. Furthermore, as appears from FIG. 2, the drivebelt 11 abuts the belt pulley 10 substantially radially outside thelower bearing member 5.

The re-circulating air stream with the oil mist may thus pass throughthe shielding member 23 via the lower opening 27, through the lowerbearing member 5 and out through the channels 21 of the upper part ofthe belt pulley 10. The air stream with the oil mist may however notpass into the channel 25 defined by the shielding member 23 thanks tothe sealing arrangements 28 and 31. However, an air stream from the airof the surroundings of the drive unit 1 may pass through the passages 12and 24 and the channel 25. In such a way, further cooling of the oilmist may be obtained and at the same time, the cooling of the lowerbearing member 5 may be improved.

The drive belt 11 disclosed will thereby act as a pump member andcontribute to driving such an air stream through the channel 25. Thepart of the drive belt 11 which runs inwardly in the channel 25 willthereby force an air stream into the channel 25 and the part of thedrive belt 11 running outwardly in the channel 25 will force an airstream out of the channel 25. In order to improve the air flow throughthe channel 25, a wall member 32 is provided substantially centrally inthe channel 25 in such a way that the channel 25 is divided into twopartial-channels. The wall member 32 extends in a substantially axialand radial plane with respect to the axis z of rotation from an area inthe proximity of the belt pulley 10 to an area in the proximity of thepassage 12. The drive belt 11 thus runs inwardly in one of thepartial-channels and outwardly in the other partial-channel.

It is to be noted that channel 25 does not necessarily need to extendtransversely through the inner space 7, 8 defined by the casing 6, i.e.merely one of the passages 12 and 24 is necessary. It is also possibleto increase the cooling effect via the shielding member 23 by means of afan member arranged to increase the air flow through the channel 25.

Furthermore, also the shielding member 23 may be provided with flangesor any similar surface-increasing members, which extend into the channel25 and/or into the inner space 7, 8 defined by the casing 6.

The present invention is not limited to the embodiment disclosed but maybe varied and modified within the scope of the following claims.

What is claimed is:
 1. A drive unit (1) for a centrifuge rotor (2) of acentrifugal separator, comprising a drive shaft (3), arranged to supportsaid centrifuge rotor (2) and rotatably journalled around an axis (z) ofrotation, a casing (6), which forms an inner space for the drive shaft(3), a drive motor shaft (9) which is provided outside the casing (6)and connected to the drive shaft (3) by means of a transferring member(11) extending through a first passage (12) in the casing (6), at leastone shielding member (23), which is provided inside the casing (6) insuch a manner that the part of the transferring member (11) which islocated inside the casing (6) is shielded from the inner space, andwherein the shielding member (23) forms a channel (25), which extendsthrough the casing (6) and is shielded from the inner space of thecasing (6); and wherein the shielding member (23) includes an upperopening (26) and a lower opening (27), and the drive shaft (3) extendsthrough the shielding member (23) through the upper and lower openings(26, 27); and wherein sealing member (28, 31) are provided between thedrive shaft (3) and said upper and lower openings (26, 27).
 2. A driveunit according to claim 1 wherein the shielding member is connected tothe casing.
 3. A drive unit according to claim 1 wherein the shieldingmember (23) has an elongated shape with a longitudinal axis, whichextends substantially radially with respect to the axis (z) of rotation.4. A drive unit according to claim 1 wherein the shielding member (23)extends substantially diametrically through the casing (6) with respectto the axis (z) of rotation.
 5. A drive unit according to claim 4,wherein the drive shaft (3) is rotatably journalled in at least onebearing member (5), which is located radially inside the transferringmember (11).
 6. A drive unit according to claim 1 wherein thetransferring member includes a drive belt (11) which engages the driveshaft (3) via a belt pulley (10), which is provided on the drive shaftand thus is located inside the shielding member (23).
 7. A drive unit(1) for a centrifuge rotor (2) of a centrifugal separator, comprising adrive shaft (3), arranged to support said centrifuge rotor (2) androtatably journalled around an axis (z) of rotation, a casing (6), whichforms an inner space for the drive shaft (3), a drive motor shaft (9)which is provided outside the casing (6) and connected to the driveshaft (3) by means of a transferring member (11) extending through afirst passage (12) in the casing (6), at least one shielding member(23), which is provided inside the casing (6) in such a manner that thepart of the transferring member (11) which is located inside the casing(6) is shielded from the inner space, and wherein the shielding member(23) forms a channel (25), which extends through the casing (6) and isshielded from the inner space of the casing (6); wherein the casing (6)includes a second passage (24) diametrically opposite to the firstpassage (12), and wherein the shielding member (23) extends between thetwo passages (12, 24) in such a way that the channel 25) extends throughthe casing (6).
 8. A drive unit for a centrifuge rotor (2) of acentrifugal separator, comprising a drive shaft (3), arranged to supportsaid centrifuge rotor (2) and rotatably journalled around an axis (z) ofrotation, a casing (6), which forms an inner space for the drive shaft(3), a drive motor shaft (9) which is provided outside the casing (6)and connected to the drive shaft (3) by means of a transferring member(11) extending through a first passage (12) in the casing (6), at leastone shielding member (23), which is provided inside the casing (6) insuch a manner that the part of the transferring member (11) which islocated inside the casing (6) is shielded from the inner space, andwherein the shielding member (23) forms a channel (25), which extendsthrough the casing (6) and is shielded from the inner space of thecasing (6); wherein the transferring member includes a drive belt (11)which engages the drive shaft (3) via a belt pulley (10), which isprovided on the drive shaft and thus is located inside the shieldingmember (23); wherein the drive unit further includes a wall member (32),which is substantially centrally provided in said channel (25) in such amanner that the channel is divided into two partial-channels and thatthe drive belt (11) runs inwardly in one of the partial-channels andoutwardly in the other partial-channel.
 9. A drive unit according toclaim 8, wherein the wall member (32) extends in a substantially axialand radial plane with respect to the axis (z) of rotation from an areain the proximity of the belt pulley (10) to an area in the proximity ofsaid passage (12).